Wax refining



Nov. 28, 1950 R. W. PRESSING ET AL WAX REFINING Filed Sept. 10, 1948 20/ I0 35% CRUDE VEGETABLE LEAFY MATTER WAX POW D E R PART BY WT.

DRY SCREEN PTIONAL) 29 WATER 2.5m 25 PARTS BY WT. POWDER AGITATE FOR w TT I E APPROXIMATELY /5 MIN.

WET SCREEN IOPTIONAD HORIZONTAL, CON/0.4L 50m LEAFY MATTER OFF CENTRFUGE com/mucus D/SGHARGE TYPE "BORRA" ROTARY VACUUM F/L rm DE WATER 0/? HAS/(E T GENTR/FUGE APPROXIMATELY 40% MOISTURE AIR 0)? VACUUM DRY BELOW DRY MELT/N6 P0,; URMELTAND B011. OFF WATER J/VVE/VTURS WAX PQWDER R.W.Pressin|g LEAFY MATTER Patented Nov. 28, 1950 UNITED STATES PATENT OFFICE WAX REFINING Robert W. Pressing and Bradley Pettibone, Racine, Wis., assignors to S. C. Johnson & Son,

Inc, Racine, Wis.

6 Claims.

This invention relates to the manufacture of raw material wax. More specifically, it relates to an improved process for removing known waxy matter from crude vegetable wax powder.

Many vegetable waxes such as esparto grass wax, carnauba wax and ouricury wax are removed from the plants by mechanical means and are, therefore, in the form of crude wax powder containing small particles of crude wax together with particles of other vegetable matter. in the case of carnauba wax, the leaves are out from the carnauba palm and allowed to dry. The wax remains largely enclosed in the crevices of the dryand shrunken leaves. When the wax powder is removed from the leaves, a large amount of leafy matter becomes mingled with the wax particles. This leafy matter is also in powdered form of a particle size, shape and mass com parable to that of the wax powder from which it can scarcely be distinguished.

Various methods and apparatus have been proposed for the removal of this leafy matter, or borra, as it is known in Brazil. Typical of the apparatus used are screeners such as the Gyro Whip, described in U. S. Patent No. 2,159,549. the Abbe described on page 6 of Bulletin No. 42 published by the Abbe Engineering Company of New York, and the commercial screening method as disclosed in U. S. Patent to Johnson et a1. N0.

2,275,630. The crude wax powder may be subjected to such air flotation separators as the Raymond described in U. S. Patent No. 1,783,359.

Although the above methods have contributed considerably to the production of a light-colored wax, nevertheless, they are only capable of reducing the leafy matter or borra from its original content of 20-35% to a minimum of 12%. The presence of the remaining borra is highly undesirable in that it tends to darken the wax upon melting.

Now, in accordance with our invention we have developed an improved process for removing leafy matter or borra from crude vegetable wax powder. This process, which is limited to the treatment of crude vegetable wax powder, which has not been melted in the production thereof, comprises wetting the vegetable wax powder with at least 2% parts of water to each part of said powder, introducing said wax-water mixture into a centrifugal force separation zone, discharging wax from said zone in the form of a liquid slurry,

discharging borra from said zone as a solid, and recovering said wax from said slurry.

Now, having indicated in a general way the nature and purpose of this invention, the following examples will illustrate the invention. It is to be understood, however, that such examples are presented merely as illustrations of the invention and are not to be construed as limiting the same. In the examples, the ingredients are given by weight unless otherwise indicated.

Example 1 One hundred parts of crude carnauba wax powdercontaining 25% borra was screened so as to separate the large particles of foreign matter from the powder. After this screening the powder retained a borra content of approximately 23%. The dry crude wax powder was then fed into suitable vessels where the powder was thoroughly wet and agitated with about 1000 parts of water for a period of approximately 15 minutes. The crude wax-water slurry was then fed into a horizontally elongated centrifugal force separator having a conical-shaped bowl which rotated to create in the separation zone a centrifugal force of approximately 2,500 times gravity. lhe was: was discharged therefrom in the form of a slurry after a period of about seconds. The discharged slurry contained about 93% water and was placed in a basket centrifuge for dewatering.

Example 2 One hundred parts .of crude carnauba wax powder containing 25% borra was screened so as to separate the large particles of foreign matter from the powder. This screening was too coarse to reduce the borra content of the powder. The dry crude wax powder was then continually fed into suitable vessel where it was thoroughly wet and agitated with about 10 times its weight of water to form a slurry. After an agitating period of approximately 15 minutes, the slurry was continually withdrawn by means of pumps and conducted into a centrifugal force separator (of the type described in Example 1) where it was tr used for a period or" about 30 seconds and then discharged as a wax-water slurry. The discharged slurry contained 3% bcrra by weight of the crude wax powder and 94% of the slurry weight cons-is ed of water. To dewater, the slurry was processed in a rotary vacuum filter of conventional type and the resulting wax press cake contained about 40% of water. Thereupon, the wax powder was further dried by exposure to the atmosphere.

In the above examples, there has thus been illustrated our improved process for removing leafy matter or borra from crude vegetable wax powder without the utilization of the conventional series of screening and air flotation devices. Both Examples 1 and 2 illustrate the treatment of dry crude vegetable wax powder having a borra content of approximately 25% which upon treatment was reduced to less than 4%.

The wetting of the surface of the dry crude vegetable wax powder prior to its introduction into the centrifugal force separation zone is essential, since without it little separation of the borra can be achieved. It should be appreciated that the mode of wetting is not imperative. A suitable vessel or plurality of vessels, may be used to wet the crude powder either in a batch or continuous system. Agitation may be employed and such agitation may be rendered by mechanical means or aeriation and may be manual or automatic.

Ordinarily the ratio of water to crude wax powder will be from about 2 /2 to 25 parts of water to 1 part of wax by weight. While the ratio of water to wax may be increased over that amount, the additional Water does not improve the efficiency of the process and provides additional recovery problems. However, it is essential to use at least 2 parts of water per part of wax as this ratio provides the minimum amount of water adequate for wetting.

Ordinarily in carrying out this process, cold water or water of a temperature of about 20 to 25 C. may be used. The use of hot water or water of a temperature of more than 70 C. sometimes results in emulsification of the wax in the water and interferes with an efiicient separation of the borra from the wax. Therefore, the use of water of a temperature of not more than 70 C. is recommended. Under no circumstance should water be employed which bears a temperature as high as the melting point of the crude wax powder.

If desired, the slurry after the wetting step, may be passed through a screen to remove large leaf fibers before progressing to the centrifugal force filter.

The centrifugal force separator may be of varying design or construction but we have found to be satisfactory a horizontally elongated separator, having a conical-shaped bowl which rotates at a speed sufficient to create in the separation zone a centrifugal force in the range of 1000 to 10,000 times gravity. A screw-conveyor, conforming to the inner contour or periphery of the bowl rotates with it, but at a different speed. An outlet or plurality of outlets are positioned at one end of the bowl to discharge the wax-water slurry while the borra is discharged at the other end of the bowl. As shown in the examples, this separator reduces the borra content of the crude wax powder to 24%, depending upon the wax and borra particle size the specific gravity and viscosity of the slurry.

The dewatering of the slurry may be accomplished by various methods which are well known in the art, such as subjection to rotary vacuum filtration as shown in Example 2 or basket centrifuging as disclosed in Example 1 or by filter-pressing.

As shown in the examples, the moist wax after dewatering contains approximately 40% Water. Thiscontent may be reduced by breaking the wax cake into small lumps, and air-drying in open trays. The moist wax may be heated and the water boiled off or the wax may be melted and subsequently dewatered by centrifuging.

This process for purifying crude vegetable wax powder may be performed as a batch system or as illustrated in Example 2, the entire treatment may be a continual process. In the latter case, the various steps or stages, or the apparatus used to accomplish such steps, are connected by means of pipes, the slurry being motivated by means of recycling centrifugal or gear pumps.

If desired, a holding tank may be positioned intermediate the various steps. These tanks, if employed either in the batch or continuous system, are preferably provided with agitating means to maintain the crude wax powder in suspension.

While the examples have illustrated the separation of leafy matter or borra from crude carnauba wax powder, it will be understood that this process is equally applicable to other vegetable wax powders such as esparto wax and ouricury wax which are obtained from the plant fibers in the form of a powder.

By the practicing of our invention, a lightcolored wax is obtained which greatly increases the commercial uses and value of the vegetable wax. It is anticipated that the dry vegetable wax powder may be treated with adsorbents and melted, thus obtaining a wax of sufiicient lightness to eliminate the necessity of bleaching with chemicals which are well known in the art. While chemical bleaching agents often provide a lightness of color, the resulting alteration of the structural and chemical nature of the original wax is detrimental where the particular characteristics of the original wax is desired.

We claim:

1. A process for purifying crude vegetable wax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax powder with at least 2 parts by weight of water, having a temperature of less than 70 C., to each part by weight of wax powder, introducing said crude wax-water mixture into a centrifugal force separation zone, discharging wax from said zone in the form of a liquid slurry, discharging borra from said zone as a solid, removing the water from said slurry and mechanically recovering solid wax.

2. A process for purifying crude vegetablewax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax power with at least 2 parts by weight of water, having a temperature of less than 70 0., to each part by weight of wax powder, continuously introducing said crude waxwater mixture into a centrifugal force separation zone, continuously discharging wax from said zone in the form of a liquid slurry, continuously discharging borra from said zone as a solid removing the water from said slurry and mechanically recovering solid wax.

3. A process for purifying crude vegetable wax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax powder with from 2% to 25 parts by weight of water, having a temperature of less than 70 C., to each part by weight of wax powder, introducing said crude wax-water mixture into a centrifugal force separation zone, discharging wax from said zone in the form of a liquid slurry, discharging borra from said zone as a solid, removing the water from said slurry and mechanically recovering solid wax.

4. A process for purifying crude vegetable wax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax powder with from 2 to 25 parts by weight of water, having a temperature of less than 70 0., to each part by weight of wax powder, continuously introducing said crude waxwater mixture into a centrifugal force separation zone, continuously discharging wax from said zone in the form of a liquid slurry, continuously discharging borra from said zone as a solid, removing the water from said slurry and mechanically recovering solid wax.

5. A process for purifying crude vegetable Wax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax powder with at least parts by weight of water, having a temperature of less than 70 0., to each part by weight of wax powder, introducing said crude wax-water mixture into a centrifugal force separation zone, discharging wax from said zone in the form of a liquid slurry, discharging borra from said zone as a solid removing the water from said slurry and mechanically recovering solid wax.

6. A process for purifying crude vegetable wax powder which has not been melted in the production thereof, comprising wetting the crude vegetable wax powder with at least 10 parts by weight of water, having a temperature of less than C., of water, having a temperature of less than 70 C., to each part by weight of wax powder, continuously introducing said crude wax-water mixture into a centrifugal force separation zone, continuously discharging wax from said zone in the form of a liquid. slurry, continuously discharging borra from said zone as a solid removing the water from said slurry and mechanically recovering solid wax.

ROBERT W. PRESSING. BRADLEY J. PETTIEONE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Science News Letter for May 20, 1944 page 331. 

1. A PROCESS FOR PURIFYING CRUDE VEGETABLE WAX POWDER WHICH HAS NOT BEEN MELTED IN THE PRODUCTION THEREOF, COMPRISING WETTING THE CRUDE VEGETABLE WAX POWDER WITH AT LEAST 2 1/2 PARTS BY WEIGHT OF WATER, HAVING A TEMPERATURE OF LESS THAN 70*C., TO EACH PART BY WEIGHT OF WAX POWDER, INTRODUCING SAID CRUDE WAX-WATER MIXTURE INTO A CENTRIFUGAL FORCE SEPARATION ZONE, DISCHARGING WAX FROM SAID ZONE IN THE FORM OF A LIQUID SLURRY, DISCHARGING BORRA FROM SAID ZONE AS A SOLID, REMOVING THE WATER FROM SAID SLURRY AND MECHANICALLY RECOVERING SOLID WAX. 